This invention relates to an improved biological treatment of wastewater and provides a method and apparatus for upgrading the efficiency of existing wastewater treatment plants and for new facility construction. More specifically, the invention is concerned with employing microscreens or microstrainers, hereinafter referred to as "microscreens," both before and after treatment utilizing a rotatable, partially-submerged contactor in new or existing concrete tankage.
The use of microscreens in conjunction with a rotating biological contactor is described by Pak-Shing Cheung, et al., in Water Research, Volume 14, pages 67-75 "Investigation To Replace The Conventional Sedimentation Tank By A Microstrainer In The Rotating Disc System." It is also known in the wastewater treatment field to employ air driven rotating biological contactors as shown in U.S. Pat. No. 4,093,539. Further, the use of fluid including recirculating fluid to drive the rotating biological contactors is also well known.